This invention relates to a heat-insulating case with a light weight and a high heat-insulating characteristic, the case being in an integrated structure of a high density layer and a low density layer, and to a process for preparing the said heat-insulating case through one step according to reaction injection molding using a liquid raw material of high chemical reactivity.
Plastic structures comprised of an injection-molded base of, for example, ABS (acrylonitrilebutadienestyrene) resin or polypropylene resin, and a single or laminated heat-insulating foam layer of, for example, polyethylene foam, polystyrene foam or polymethane foam, as bonded to the base, have been so far used for cases for air conditioners of controlling the room temperature and humidity of automobiles. A vacuum-molded base of polypropylene resin sheet is also used in place of the injection-molded base of ABS resin.
However, these structures not only require much labor and time in molding work of the base and foam as well as in the bonding work, but also a distinguished heat-insulating efficiency cannot always be obtained in spite of the increased number of the required parts.
A refrigerator which can be loaded on a car and also can be transported by itself when not loaded on it has not been commercially available, but the case for such refrigerator could be prepared basically according to the conventional art, for example, by individually molding an inner case structure and an outer case structure of the ordinary plastic and by injecting polyurethane into between these case structures to obtain a heat-insulating case, but such art would not be efficient in the required molding facility, a plurality of required materials, and increased numbers of process steps and required parts, as in the case for the said air conditioners